Chapter 1 Tip Sheet

1D Truth and Logic

  • Truth analysis: Determines whether the information in the premises is accurate, correct, or true. Truth analysis is about statements.
  • Logical analysis: Determines the strength with which the premises support the conclusion. Logical analysis is about arguments.

1F Deductive Arguments: Validity and Soundness

  • Valid Argument: In a valid deductive argument, it is impossible for the conclusion to be false assuming the premises are true. If the premises actually are true, then the deductive argument is sound as well.

A deductive argument reads: If the premises are assumed to be true, then is it impossible for the conclusion to be false? If yes, then the argument is valid. Check if all the premises are true. If yes, then the argument is sound. If not, then the argument is unsound. If no, then the argument is invalid and is unsound.

1G Inductive Arguments: Strength and Cogency

  • Strong argument: In a strong inductive argument, it is highly probable that the conclusion is true assuming the premises are true. If a strong argument has actually true premises, then it is cogent as well.

Inductive argument has two questions, that read: a, If the premises are assumed to be true, then is it improbable for the conclusion to be false? b, Does the probable truth of the conclusion follow from the premises? If yes, then strong, are all the premises true. If yes, then cogent. If not, uncogent. If no, then weak, leads to uncogent.

1H Reconstructing Arguments

  • Enthymemes: Arguments are not always presented completely; sometimes a premise or conclusion is missing. The knowledge and skill set that enables you to recognize arguments will help you reconstruct an incomplete argument. For example,
    • He’s a contractor, so he won’t get the job done on time.
    • He’s a contractor. [Contractors never get jobs done on time.] So he won’t get the job done on time.
  • Rhetorical language: Sometimes, arguments are implicitly asserted by appearing in the form of a question, conditional claims or in disjunctions. In each case, your goal is to clarify and make explicit what’s only implicitly being asserted or argued. For example, you can remove a question mark and rewrite the sentence so that the point of the argument, or the conclusion, is clear.
    •  
    • You have not been training for that marathon like everyone else. Do you really think you’ll be able to participate in it?
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    • You have not been training for that marathon like everyone else. [Therefore, you will not be able to participate in it.]
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